1. Field of the Invention
The present invention relates to a drive apparatus for moving a certain object (driven object) in a desired direction, and an XY drive apparatus on which said drive apparatus is equipped.
2. Description of the Prior Art
An example of the prior art having this type of drive apparatus is the XY drive apparatus indicated in FIG. 1.
As indicated in FIG. 1, said XY drive apparatus is composed of X table 1 installed on the floor or a mounting frame in a workshop, and Y table 2, that is supported and moved by said X table 1 and arranged to be intersecting with said X table 1. Furthermore, since X table 1 and Y table 2 mutually have nearly the same constitution, the following detailed explanation will be provided with respect to X table 1 only, and an explanation of Y table 2 is omitted. However, those constituent members of Y table 2 that correspond to the constituent members of X table 1 are indicated using the same reference numerals.
As indicated in FIGS. 1 and 2, X table 1 has a long, roughly rectangular plate-shaped base 13, and side plate 14 is provided on both sides of said base 13. Mounting member 15 is attached to one end of base 13, and motor 16 and sensor connector 17 are mounted on said mounting member 15. In addition, stationary bearing mechanism 18 is provided on the other end of base 13, and ball screw 19 is supported by said stationary bearing mechanism 18. In addition, the torque of motor 16 is transmitted to ball screw 19 through coupling 20. Furthermore, as is well known, ball screw 19 is composed of a feeding screw in the form of male screw 21, and a female screw in the form of nut 22 that screws onto male screw 21 by means of a ball (not shown), and moves as a result of rotation of said male screw 21.
As indicated in FIG. 2, one end of male screw 21 is supported by bearing 18a equipped on stationary bearing mechanism 18 while allowing to rotate freely. The other end 21a is formed to be narrower than the threaded portion, and is supported by bearing 23a equipped on bearing unit 23 while allowing to rotate freely. In addition, the gap in the axial direction between this other end 21a and bearing 23a is eliminated by tightening of bearing nut 24 resulting in regulation of movement in the axial direction by male screw 21, and the torque of motor 16 is transmitted as a result of being linked to coupling 20.
On the other hand, nut 22 is fastened by bolts (not provided with reference numerals) to the end of moving table 27 having a roughly T-shaped cross-section as indicated in FIG. 3. This moving table 27 is formed of a size that allows it to be contained within the width of side plate 14, and two table projections 27a are formed in parallel on the upper surfaces of both its left and right sides, that protrude above the upper surface of side plate 14. Above-mentioned Y table 2 is attached to these table projections 27a with bolts (not shown). Furthermore, as indicated in FIGS. 1 and 3, cover 28, acting to prevent entrance of dust and debris, is arranged to be positioned to the inside of both of these table projections 27a. In addition, as indicated in FIG. 3, stopper 29, having a prescribed length, protrudes from one end of moving table 27. This stopper 29 is for restricting movement of moving table 27 to the end position in the axial direction of said moving table 27.
As indicated in FIGS. 2 and 3, moving table 27 is supported by a pair of sliding members 31. These sliding members 31 are formed to have a cross-section roughly in the shape of a "U", and slide along guide rails 32 mounted on mounting surfaces 13a of base 13. A guiding device that guides moving table 27 in the direction in which is to drive (X) by these sliding members 31 and guide rails 32. Furthermore, two grooves 13b are formed in parallel with the above-mentioned mounting surfaces 13a on base 13, and sensors 34, for detecting the stroke limit and origin position of moving table 27, are mounted at the prescribed locations of said grooves 13b.
The following provides an explanation of the operation of the XY drive apparatus composed of the above-mentioned constitution.
Firstly, electrical power is supplied to each motor 16 of X table 1 and Y table 2.
When an electrical power voltage is applied to motor 16 of X table 1, said motor 16 turns resulting in torque being transmitted to male screw 21 of ball screw 19 through coupling 20 and so forth. As a result of this rotation of male screw 21, moving table 27 mounted to nut 22 moves linearly in the X direction along guide rails 32. Accordingly, Y table 2 mounted on said moving table 27 also moves in the X direction.
On the other hand, since Y table 2 is composed in the same manner as the above-mentioned X table 1 so moving table 27 (see FIG. 1) equipped on it linearly moves independently in the Y direction, by controlling the operation of said X table 1 and Y table 2 by a control circuit not shown, workpieces in the form of electronic components placed on moving table 27 of Y table 2 can be moved two-dimensionally as desired.
As described above, in the drive apparatus of the prior art, a driven object in the form of moving table 27 is driven by ball screw 19. However, the generation of deflection within those surfaces of nut 22 perpendicular to the shaft center of male screw 21, or in other words, in the radial direction, accompanying rotation of said male screw 21, cannot be avoided in ball screw 19. Thus, the electronic components and so forth on moving table 27 are subjected to pitching and yoking resulting from this deflection of nut 22, thus resulting in the shortcoming of having a detrimental effect on straightness and other factors related to accuracy of positioning or orientation of said electronic components and so forth.